| Glycyrrhizia uralensis Fisch.(GuF.) was one of traditional herbal medicines in China,whose medicinal parts were roots and rhizomes that contained the most significant secondary metabolic component for GuF.’s efficacy--glycyrrhizic acid(GA).The content of GA was standardized to assess the quality of GuF. as medicinal material.GuF.’s root extended deeply underground and interacted closely with the rhizosphere.The root exudates of GuF. that acted as a bridge linking root and rhizosphere,as well as the influence of these exudates’accumulation in rhizosphere to GuF.’s quality,however,gained less attention.Given that,this research utilized gas chromatography-mass spectrometry(GC-MS) and high performance liquid chromatography(HPLC) to primarily identify the ingredients and corresponding content in GuF.’s root exudates.On this basis,one of GuF.’s root exudates with a relatively high content-oxalic acid--was chosed to apply on GuF. plants. With the utilization of Real-time PCR,the influence of oxalic acid treatment to two key enzyme genes(GuSQSland GubAS) in biosynthesis of GA was investigatedThere came a.preliminary conclusion that oxalic treatment with high concentration (>≥1 × 10-4mol/L) or low concentration (≤1×10-7mol/L) could significantly inhibit the biosynthesis and accumulation of GA in GuF. seedlings,and the existence of oxalic acid could affect the biosynthesis location of GA in root of GuF.’s one-year-old seedlings.The main results were as follows:1、With the utilization of HPLC,oxalic acid and lactic acid were identified in root exudates from both seedlings and one-year-old seedlings of GuF.. Each seedling averagely released 0.096mg oxalic acid and 0.061mg lactic acid during one day and each one-year-old seedling released 0.032mg oxalic acid and 0.346mg lactic acid.2^ With the utilization of GC-MS,35 ingredients were isolated from root exudates of GuF. seedlings,among which 15 were identified. The root exudates mixture consisted of esters,hydrocarbons,benzene,phenol and a small amount of ethers, amines,aldehyde,thiazole,et;3-. With the utilization of GC-MS,60 ingredients were isolated from rhizosphere soil of GuF. three-year-old seedlings,among which 40 were identified. These 40 compounds were mainly alcohols,esters,hydrocarbons,ethers, ketones,amines,et.21 ingredients were isolated from non-rhizosphere soil and all of them had been identified.These 21 compounds could be found in rhizosphere soil and were mainly alkanes.which accounted for 90.476% of all.4, In short term(3d) treatment,oxalic acid treatment with serial concentration gradients (1× 10-3、 1 × 10-4、1×10-5、1×10-6、1× 10-7mol/L) to GuSQSl gene in GuF. seedlings showed a trend of low-repressing and high-promoting. While to GubAS gene it showed low-repressing, high-repressing and intermediate concentration insignificant;5,1 ×10-4 mol/L oxalic acid treated GuF. seedlings for72h and it significantly repressed the expression of GuSQSl gene but the influence on GubAS gene was insignificant.This indicated that oxalic treatment in such concentration might have little influence on biosynthesis of GA in root of GuF. seedlings;In terms of the treatment time,GuSQSl gene expressed relatively high during 12h to 72h andGubAS gene during 24h to 48h.This indicated that later period of treatment might be rapid period for GA biosynthesis in GuF. seedlings.6,1 ×10-4 mol/L oxalic acid treated GuF.one-year-old seedlings for 5w and it significantly promoted the expression of GuSQS1 and GubAS genes in xylem but repressed the expression of GubAS gene in hairy lateral root.This indicated that oxalic treatment in such concentration might promote the biosynthesis of GA in xylem of GuF. one-year-old seedlings,meanwhile repress the biosynthesis of GA in hairy lateral root;In terms of the treatment time,GuSQS1 gene in xylem and phloem reached a highest expression on the 3rd week,GubAS gene in xylem and hairy lateral root reached a highest expression respectively on the 3r1 week and 4th week.This indicated that the 3rd week to 4th week of oxalic acid treatment might be rapid synthesis period for GA in root of GuF. one-year-old seedlings.7、During treating period in this study,with GuF. plants’ growth and adaptation with environment,there might be rapid synthesis period and slow synthesis period for GA in root of GuF.,and oxalic acid treatment might affect the time of these two phases.8、Two key enzyme genes’expression showed obvious synchronism,once again confirming the synergistic effect between these two enzymes during biosynthesis pathway of GA. |
PDF Full Text Request